AttributeError: can't set attribute funnel_viz_type

[sentry-io]

Sentry Issue: POSTHOG-35A

AttributeError: can't set attribute
  File "rest_framework/views.py", line 506, in dispatch
    response = handler(request, *args, **kwargs)
  File "ee/clickhouse/views/insights.py", line 69, in funnel
    response = self.calculate_funnel(request)
  File "posthog/decorators.py", line 47, in wrapper
    result = f(*args, **kwargs)
  File "ee/clickhouse/views/insights.py", line 80, in calculate_funnel
    filter.funnel_viz_type = FunnelVizType.TRENDS

[macobo]

cc @neilkakkar this is caused by #4946

[Twixes]

Since Neil is off today I allowed myself to fix this in #4978. :)